This invention relates generally to a gas compressor having a dry gas sealing arrangement mounted on a compressor shaft and more particularly to a centering device for controlling the concentricity between the compressor shaft and the dry gas sealing arrangement.
Past practice has incorporated thin sheet metal strips or shims positioned around the periphery of a shaft, with the dry gas sealing arrangement pressed over the strips and shaft as a method or attempt to center the dry gas sealing arrangement on the shaft. Common practice was to form dimples or other structures having peaks and valleys in the strips in an attempt to center the dry gas sealing arrangement about the shaft.
During operation, the elasticity of the structure having the dimples, peaks and valleys formed therein was lost and the centering ability of the strips have been known to fail. When the elasticity of the structure is lost, the dry gas sealing arrangement becomes unstable, moves off center and causes the components of the gas compressor to rotate eccentric. The eccentric rotation results in unbalance and effects the operation of the gas compressor to the extent that operation thereof must be discontinued. Thus, the gas compressor must be pulled off line and repaired.
The above systems used therewith are examples of attempts to control the concentricity of dry gas sealing arrangement.
The present invention is directed to overcome one or more of the problems as set forth above.
In one aspect of the invention, a centering device is adapted to center a member on a shaft. The shaft has an outer profile. The centering device is comprised of a generically cylindrical sleeve having a first end and a second end. The sleeve has an inner surface and an outer surface defined between the first end and the second end. A first inner protrusion is axially spaced from the first end a preestablished distance and extends radially inward from the inner surface. A second inner protrusion is axially spaced from the second end a preestablished distance and extends radially inward from the inner surface. A first outer protrusion is axially spaced from the first end a preestablished distance and extends radially outwardly from the outer surface. The first outer protrusion is interposed the first end and the first inner protrusion. A second outer protrusion is axially spaced from the second end a preestablished distance and extends outwardly from the outer surface. The second outer protrusion is axially interposed the first inner protrusion and the second inner protrusion. The first inner protrusion and the second inner protrusion are in contacting relationship with the outer profile of the shaft. And, the first outer protrusion is cantilevered about the outer profile of the shaft and the second outer protrusion is mid-supported about the outer profile by the first inner protrusion and the second inner protrusion.
In another aspect of the invention, a method of centering a member on a shaft having a centering device positioned therebetween is disclosed. The shaft is comprised of a first end, a second end and an outer profile defining a first raised portion positioned near the first end and a second raised portion positioned between the first raised portion and the second end. The first raised portion has a preestablished diameter and the second raised portion has a preestablished diameter larger than the preestablished diameter of the first raised portion. The centering device is comprised of a first end and a second end. An inner surface and an outer surface is defined between the first end and the second end. A first inner protrusion extends radially inward from the inner surface, has a preestablished diameter and is positioned near the first end. A second inner protrusion extends radially inward from the inner surface, has a preestablished diameter larger than that of the preestablished diameter of the first inner protrusion and is positioned between the first inner protrusion and the second end. A first outer protrusion extends radially outward from the outer surface, has a preestablished diameter and is positioned near the first end. A second outer protrusion extends radially outward from the outer surface, has a preestablished diameter larger than the preestablished diameter of the first outer protrusion and is positioned between the first outer protrusion and the second end. And, the member is comprised of a first end, a second end, a inner surface extending between the first end and the second end of the member. A first protrusion extends radially inward from the inner surface of the member, has a preestablished diameter and is positioned near the first end of the member. A second protrusion extends radially inward from the inner surface of the member, has a preestablished diameter larger than that of the preestablished diameter of the first protrusion and is positioned between the first protrusion and the second end. The method of assembling comprising the following steps: attaching an assembly tool to the centering device; heating the centering device and the assembly tool; positioning the centering device and assembly tool onto the first end of the shaft; positioning the first inner protrusion and the second inner protrusion in axial alignment with the first raised portion and the second raised portion respectively; allowing the assembly tool and the centering device to cool, thus, frictionally engaging the first inner protrusion with the first raised portion and the second inner protrusion with the second raised portion respectively; removing the assembly tool; positioning the member onto the first end of the shaft and the first end of the centering device; and positioning the first protrusion and the second protrusion on the member in axial alignment with the first outer protrusion and the second outer protrusion on the centering device respectively.